Before I start I'd like to just state as of this I've only seen S1 of Aikatsu Friends so I'm still pretty new into the franchise.
Story Wise: 6.5
I may have given it a 7 in the but that's only because the rating system allows but I don't believe it deserves a 6.
To be honest I'm very mixed on aspects of Aikatsu Stars. The first season 1-50 was really enjoyable as we got the growth of all the characters who were more than just background characters. I tend to classify characters in to 3 groups. Main, Main Supporting, and Sub Supporting. Sub
supporting being characters that show up but don't have any major impact on the story. S2 though is where I take major issue the story and it faces demerits in my book. S2 story pushes an antagonist with some very clear issues and this detracts as a whole the further you go into s2.
It's more of a 7.5ish just because you can tell times when they cut corners to save for bigger moments within the ep/arc. Only other issue is certain contrasting design aspects in a couple crossover EP.
Main character and Main Supports do get a lot of attention as you would hope in a 100 ep series. My only real complaints is a certain character and then how they seem to be more than willing to do other characters dirty in my opinion. There were a good few ep I watched where I felt they dunked on characters for the sake of it.
Sound: 9 as a whole
One of the things a friend kept going on about in previous Aikatsu was how the songs were more varied than in Friends. I can agree and disagree. They largely used the same formula as what I saw in Friends but we have a more varied cast in Stars. Music as a whole was great though.
Enjoyment: 8.5 in reality but again MAL rating system only allows by whole point intervals.
S2 has some really solid moments but again is drug down by a character and to be honest initially those around her but they all get their own great moments.
I said what I had in each section. Would I recommend this? Depends to be honest. It's a franchise technically aimed at little girls on top of being an idol anime on top of being 100 ep. If you already like ani-idol stuff I'd say yes go for it, if not it's honestly a hard sell.